1. Field of the Invention
The present invention relates to a decorating sheet having a pattern that gives a visually three-dimensional sensation, to a decorated molded product using the decorating sheet, and to an in-injection-mold decorating method for producing a decorated molded product.
2. Background Art
Decorated molded products obtained by integrating decorating sheets into the surfaces of resin molded products, adherends, are used in a variety of applications. A typical method for producing such a decorated molded product is in-injection-mold decorating that the molding of a resin into a molded product and the lamination of a decorating sheet to the resin molded product are simultaneously conducted (see the following Patent Documents 1 to 6).
In in-injection-mold decorating, the following methods (1) to (4), for example, have been employed to form, on a molded product, a three-dimensional pattern such as a pattern of the grain and vessels of wood so that the surface of the decorated molded product gives a three-dimensional sensation.                (1) A three-dimensional pattern to be embossed has been engraved, in advance, on the cavity wall of an injection mold in order to obtain a decorated molded product (a decorating sheet) having, on its surface, the three-dimensional pattern.        (2) A decorating sheet obtained by using, for its substrate sheet, a sheet of a thermoplastic resin such as an acrylic resin, and embossing a three-dimensional pattern on the substrate sheet with heat and pressure applied is employed.        (3) A printing method such as screen printing method is employed to form a three-dimensional pattern.        (4) A decorating sheet having a three-dimensional pattern is firstly prepared by raise-printing method, using ink made from a curable resin such as an ultraviolet-curing resin. Specifically, for example, at least the recesses in an intaglio roll (also referred to as a shaping plate, a plate cylinder, etc.) are filled with an ionizing-radiation-curing resin ink, and a resin sheet is brought into contact with this ink. The ink, retained between the resin sheet and the intaglio roll, is hardened by ionizing radiation, and the resin sheet is then removed from the intaglio roll. There is thus obtained the resin sheet with the hardened ink in a three-dimensional pattern (see Patent Documents 3, 4, 5, and 6, etc.).        
Patent Document 1: Japanese Patent Publication No. 19132/1975.
Patent Document 2: Japanese Patent Publication No. 27488/1968.
Patent Document 3: Japanese Laid-Open Patent Publication No. 87318/1982;
Patent Document 4: Japanese Patent Publication No. 22755/1982.
Patent Document 5: Japanese Patent Publication No. 50066/1988.
Patent Document 6: Japanese Laid-Open Patent Publication No. 32476/1995.
However, the above-described methods (1) to (4) have had the following drawbacks. The method (1) that, while conducting injection molding, a molded product is embossed in an injection mold is disadvantageous in that the face that can be embossed is limited only to the surface of the molded product. It is, therefore, impossible to form a three-dimensional pattern in the inner side of the molded product. Moreover, to previously engrave, on the cavity wall of the injection mold, a three-dimensional pattern to be embossed is essential, so that it is necessary to replace the whole injection mold, which is expensive, when the design of the pattern to be embossed is changed, even if the shape of the molded product itself is not changed. Therefore, it has not been easy to change the pattern to be embossed.
The method (2) that a thermoplastic resin sheet is used for the substrate sheet of a decorating sheet has been disadvantageous in that, when the decorating sheet is preformed in the vacuum forming step prior to the injection molding step in order to make it fit to decorate the solid faces of a molded product, the three-dimensional pattern embossed on the decorating sheet is flattened due to the heat that is used to preform the decorating sheet.
The method (3) in which a three-dimensional pattern is formed by a printing method such as screen printing method has been disadvantageous in that, since the amount of ink that is transferred is limited and small, the printed pattern is not so three-dimensional as an embossed pattern.
The method (4) that raise-printing is conducted by using an ultraviolet-curing resin or the like and an intaglio roll or the like can provide a pattern that is more three-dimensional than a pattern obtained by the above-described printing method (3). However, since ultraviolet light is usually applied from the resin sheet side in order to harden the resin in a three-dimensional pattern, a three-dimensional pattern cannot be obtained unless a transparent sheet is used for the resin sheet. Further, in the case where the decorating sheet is provided, with a decorative layer by a conventional printing method, if a three-dimensional pattern is formed before conducting printing for forming the decorative layer, empty spaces tend to occur in the printed decorative pattern because of the three-dimensional pattern.